Study On High Performance Photodetectors Based On Perovskite

Photodetectors play an important role in imaging,monitoring and signal transmission.With high mobility,high absorption coefficient and long diffusion length,the organo-metal halide perovskite make it possible to have new type of photodetectors with advantages of low cost,wide spectral response and high sensitivity.Recently,the research on perovskite based solar cell is attractive and promising,which achieved much progress till now.However,the photodetectors based on perovskite is still in its initial stage and many problems need to be solved urgently.Such as weak photoresponsivity in the near infrared and infrared region,low reproducibility and short lifetime.In this dissertation,to solve these above problems we use the high absorption efficiency of perovskite in ultraviolet and visible region,combine with monocrystalline silicon to absorb the illumination of near infrared and infrared,and eventually develope the wide spectral response photodiode based on perovskite/monocrystalline silicon planar heterojunction,it has a response region around 400¹000 nm.Then,benefit from the long diffusion length of perovskite,a planar photoconductive detector with high photosensitivity and 10⁶ on/off ratio is developed.At last,we develop a flexible wide spectrum photodetector with excellent performance by combining the flexibility of perovskite material with organic small molecular layer.At the same time,by using polyvinylpyrrolidone?PVP?to optimize the self-assembly process of perovskite film and the use of chlorine instead of pure iodine of perovskite the device reproducibility and lifetime are enhanced significantly.In detail,the conclusions and innovations of this paper are divided into three parts:On the first part,broadband photodiode based on Si/perovskite structure which combines the advantages of both silicon and perovskite is presented in this paper.This study addresses the issue of the absent of ultraviolet absorption of silicon and the near infrared absorption of perovskite.More significantly,the PVP modification process on the perovskite film shows efficiency on morphology and crystallizing control which are important for high uniformity of responsivity and reproducibility.The result shows high spectral uniformity of responsivity?uSR=0.85?on a wide spectrum ranging from 405 nm to 808 nm and the average of deviation of reproducibility is only 2.1%.Fast response time?645?s?,good on-off switching performance and high photosensitivity(I_on/I_off=1322)of the as-fabricated device are also achieved in this work.On the second part,in order to improve the high dark current and low sensitivity of the vertical structure photodetectors we report the planner structure photoconductive detector based on perovskite.We optimized the device with different electrodes and a specially modified active layer,and the performance of the device is satisfactory.The research shows an ultrahigh photosensitivity?up to 3.5×10⁶?and a low dark current?0.01 nA?.Furthermore,a high photoresponsivity of 11.5 A/W is achieved.In addition,through XPS test result this work reveals the devices with Al electrode have been proved to be suffered with serious oxidization at the roughness interface which leads to a low performance.In addition,the application of chlorine replacing the pure iodine of perovskite?CH3NH3PbI3-xClx?also has a good effect on the stability of the devices.Our work will provide a new way of research on ultrasensitive photodetectors.At last,we demonstrate for the first time a highly sensitive broadband photodetector based on porous organolead perovskite-phthalocyanine heterostructure,which has a response region of UV-NIR.Furthermore,after 1000 bends,the responsivity of the device is almost unchanged,which indicates a strong physical flexibility.Combining the properties of porous perovskite and triclinic lead phthalocyanine,the device achieves a pA level dark current and⁶00 ns response time.At the same time,the photosensitivity of the as-prepared devices reaches 10⁴.Our results offer a facile and promising route for the development of flexible and highly sensitive broadband photodetectors.